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Plus/4 CPU and TED temperatures and heatsinks

Hi, I am a longtime Commodore user and I started with a VIC-20 many years ago and I recently acquired a Plus/4. I am wondering about chip temperatures.


By the way, I have long being attracted by the Plus/4: I thought it's a neat little computer, but now it's the first time I can actually use one. I disassembled as the keyboard did not work and it and I am now cleaning it: I think that it should be working fine very soon. Since I haven't had any contact with the Plus/4 or a similar beast in the past (apart a friend that had a 16 when we were kids), I am reading all what I can on the Internet about it.

It seems that a lot of people suggest to put heatsinks on the TED chip and on the CPU to decrease failure rate.

Now, I ran the computer for testing the keyboard for maybe 15 minutes with the case open and I noticed that the CPU becomes only warm to my touch. I would not put a heatsink on it. Since this was conflicting with what plenty of people says, I decided to ask the expert, hence my message here :-)

I had an exchange of emails with Bil when I proposed my participation here and here is what he wrote to me:

Hi Davide, Welcome to C128! There are a couple of realities regarding heat and the chips of the TED series (264/Plus4/C16/ etc). The reality is that we made consumer devices that were meant to last about 3-5 years after which we would not have cared about the remaining lifetime left.

If I had spent a dollar outside of what was needed to make a system last that amount of time, it would have been considered a to be a waste of a dollar, and too many of those and I would have been relieved of my job as the mandate was to bring computers to the masses, which meant cheap.

The 264 was designed to sell for $79USD, if someone wanted an overdesigned system they could buy an IBM for a couple of thousand dollars, or even an Apple was $1200-$1800USD.

Then there is the effect of heat on chips, put bluntly if heat was a problem the chips would have died their first year. The chips that are left after 35 years are proof that heat isn't an issue. Yes I am aware that people take off the RF shield (which invalidates FCC, we had no choice) and put a heatsink n but in still air (or no convective chimney) I would submit they might actually run hotter, I have plans to test this BTW.

The REAL thing that breaks a 35 year old chip some of the time, (sometimes they just break, like your old favorite glass that chips one day) is the thermal cycle of applying power. Think of when a light bulb blows, it's when it's cold and there is a thermal shock, that creates a true physical stress on the die.

Heh, maybe the answer is we should pre-heat the chips before turning them on. >:) Think about this, it's counter intuitive unless you think about the actual failure mechanism.

The worst I am seeing right now are some people posting their theories that the chips should have been designed to run even cooler and more money spent and one person in particular has called everyone involved in the design/production processes incompetent to include process engineers, chip designers, mechanical designers, hardware engineers and purchasing agents, meanwhile they have never actually been exposed to production, design or real life physics on any level, and they simply don't listen when we explain how things really work from having been there and with experience making millions of these things.

Heh, recently someone accused us of purposely making bad chips. That was so ludicrous that I would not even respond to them.

I am completely surprised that any of the units actually work! We never ever thought about them lasting more than 10 years, or that people would care 10 years later, let alone 35. :)


I should see what happens with the circuit put for a longer time inside the case, but apparently my gut feelings weren't so wrong.

If it is useful, I can try to measure temperatures of the two chips with the board inside the case and outside of it, I have a small Pt100 probe and I think it should be feasible. I can try see if a small heatsink is effective or not.

Edited by: bilherd on 2019-02-08 14:00
Great results, basically we
Hi Bil,
Yes if you could get the
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